A device case of a portable electric device that may be used outdoors is conventionally provided with a waterproofing structure (“waterproofing case”) in order to prevent infiltration of moisture such as rainwater into the inside of the device case. When the electronic device case is bisected into a first case and a second case, the waterproofing case may be realized by inserting a linear elastic body into a fitting portion (“bonding portion”) of the first case and the second case without a gap. The linear elastic body which is inserted into the bonding portion of the first case and the second case may be either a continuous loop type elastic body or a discontinuous type elastic body which is discontinued at a middle portion thereof. The discontinuous type elastic body has a configuration in which the opposite ends of the elastic body are brought close to each other so that water may not infiltrate therefrom.
The continuous loop type elastic body is required to be fabricated according to the lengths of the bonding portions of the first case and the second case. Thus, when the shapes of the first and second cases and the lengths of the bonding portions of the first case and the second case are changed due to a design change, it is required to change the specification of the elastic body. Whereas, the discontinuous type elastic body may flexibly comply with a design change since the length of the elastic body may be readily changed even if the shapes of the cases and the lengths of the bonding portions of the first case and the second case are changed.
In the conventional technology, as for a material for the elastic body, a plastic resin such as a thermoplastic resin may be employed instead of a natural rubber or a synthetic rubber. The thermoplastic resin refers to a resin that is softened to exhibit fluidity when heated and changed into an elastic body when cooled. The thermoplastic resin may comply with various shape of the bonding portions when it is coated on the bonding portions of the first case and the second case. In addition, since the thermoplastic resin itself has adhesiveness, there are little restrictions on design even if a groove configured to allow the thermoplastic resin to extend to a waterproofing route is only partially provided. In order to cure the resin that exhibits fluidity, for example, mixing of two kinds of resins may be considered, except cooling the resin.
The waterproofing structure in which a thermoplastic resin that exhibits fluidity is coated on the boding portions of the first case and the second case also requires a structure in which the coating start point and coating finish point of the thermoplastic resin are brought close to each other to be subjected to a waterproofing processing. However, the following problems may be caused. When both the top surfaces of the solidified elastic bodies at the coating start point and coating finish point of the thermoplastic resin are pressed, the thermoplastic resin may stick out of a side surface of the case deteriorating the external appearance of the case. In order to avoid the thermoplastic resin sticking out of the case, it is required to precisely control the coating amount of the thermoplastic resin coated on the bonding portions of the first case and second case. However, the precise control of the coating amount is not easy and may cause a decline in yield.
The related art is disclosed in Japanese Laid-open Patent Publication No. 2004-108469.